Shortly after the German invasion of Norway the occupants started fortifying the coastline. This was a part of the Atlantik Wall the Germans erected all along the western coast of Europe. The once silent and calm Fjords of Norway suddenly saw hefty activity when armies of soldiers, engineers and Prisoners of War arrived. Grønsvik fortress was a smaller fort and is located by the coast near to the polar circle. This HKB (HeeresKüstenBatterie) was armed with 4 - 15,5 cm K416 French cannons with a range of 17000 meter, a 7.5 cm Field haubitze, a 5 cm KwK , mortars,mg positions,searchlights and light FlaK and it was operational in december 1942. After the war it saw use under NATO forces but today it is a small museum housed in one of the buildings on the site.

Stairways is leading down to underground bunkers and tunnels connecting different parts of the complex. The whole thing was mainly dug by local workers and a force of Polish POWs.